This application is based on and claims priority to Japanese Patent Application No. 2000-327063, filed Oct. 26, 2000, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present invention relates generally to an air induction system for a multi-cylinder engine, and more particularly to an improved air induction system that includes a plenum chamber to which multiple intake passages are connected.
2. Description of Related Art
A multi-cylinder engine typically has an air induction system including multiple intake passages that introduce air into multiple combustion chambers of the engine. Typically, the air is delivered to each combustion chamber through each intake passage in due order because each combustion cycle per cylinder occurs sequentially one by one. In some arrangements, the intake passages are coupled with a plenum chamber disposed upstream thereof. The plenum chamber primarily is used to coordinate airflow delivered to the combustion chambers through the separate intake passages.
The combustion chambers typically are formed with an engine body and pistons reciprocally disposed relative to the engine body. Normally, a valve mechanism controls the air introduction to the combustion chambers. For example, intake valves are disposed to move between an open position in which the combustion chambers are connected with the associated intake passages and a closed position in which the combustion chambers are disconnected with the associated intake passages.
In general, the movement of each piston toward a crankcase generates negative pressure. The negative pressure makes a negative pressure draws the air in the plenum chamber to the combustion chamber. Theoretically, the negative pressure makes a negative pressure wave that proceeds upstream to a free edge, e.g., a connecting portion with the plenum chamber and is reflected at the free edge. At the moment of the reflection, the negative pressure wave alters itself to a positive pressure wave and proceeds downstream to the combustion chamber. If this positive pressure wave returns to the combustion chamber at the end of the intake stroke, a large quantity of air can be charged into the combustion chamber. That is, the positive pressure wave advantageously increases the charging efficiency of the engine. The effective positive pressure wave is an inertia wave. If, at the moment when the positive pressure wave returns to the combustion chamber, the intake valve is in the closed position, the wave, still as the positive pressure wave, is reflected at the intake valve, i.e., a built-in edge, and proceeds upstream to the free edge again. This reciprocal movement of the positive pressure wave repeats between the combustion chamber and the plenum chamber. The phenomenon is a columnar vibration and the wave is a pulsation wave. The columnar vibration gradually is attenuated. If this columnar vibration is still alive until the next intake stroke of another cylinder starts and the positive pressure wave can act as the inertia wave to this intake stroke, the wave can further improve the charging efficiency of the engine.
If, however, the positive pressure wave that has been generated in the previous intake stroke of one cylinder moves back to the plenum chamber at the moment the next intake stroke of another cylinder starts, the wave can inhibit the air from moving forward. The positive pressure wave in this phase is not a useful pulsation wave and can make an undesirable valley in the engine torque characteristic. This detrimental fluctuation can occur in the engine torque characteristic per every intake stroke.
Engines constructed in accordance with the preferred embodiments of the invention provide an improved air induction system for a multi-cylinder engine that improves the engine torque characteristic. A significant feature of the preferred embodiment is that the positive pressure wave created by a previous intake stroke does not inhibit the airflow during the intake stroke of the next-to-fire cylinder.
In accordance with one aspect of the present invention, an internal combustion engine comprises an engine body. A plurality of moveable members are moveable relative to the engine body. The engine body and the moveable members together define a plurality of combustion chambers. An air induction system is arranged to introduce air into the combustion chambers. The air induction system includes a plurality of intake passages corresponding to the respective combustion chambers. A plenum chamber is coupled with the intake passages. The air is delivered to each one of the combustion chambers from the plenum chamber through each one of the intake passages in due order. The plenum chamber is divided into two sub-chambers. The intake passages are respectively connected to the two sub-chambers so that air is alternately delivered from the two sub-chambers to the combustion chambers to avoid the previous pressure wave interfering with the forward flow of air to the combustion chamber that is next in firing sequence.
In accordance with another aspect of the present invention, an internal combustion engine comprises an engine body. At least four moveable members are moveable relative to the engine body. The engine body and the moveable members together define at least four combustion chambers. An air induction system is arranged to introduce air into the combustion chambers. The air induction system includes at least four intake passages corresponding to the respective combustion chambers. A plenum chamber is coupled with the intake passages. The air is delivered to each one of the combustion chambers from the plenum chamber through each one of the intake passages in due order. The plenum chamber is divided into first and second sub-chambers. The intake passages are categorized into first and second groups. Each one of the groups includes two of the intake passages which have discontinuity in the order with each other. The first group is connected with the first sub-chamber. The second group is connected with the second sub-chamber.
In accordance with a further aspect of the present invention, an internal combustion engine comprises an engine body. A plurality of moveable members are moveable relative to the engine body. The engine body and the moveable members together define a plurality of combustion chambers. An air induction system is arranged to introduce air into the combustion chambers. The air induction system includes a plurality of intake passages corresponding to the respective combustion chambers. First and second plenum chambers are coupled with the intake passages. The air is delivered to each one of the combustion chambers through each one of the intake passages in due order. The intake passages are categorized into first and second groups. Each one of the groups includes the intake passages which have discontinuity in the order with each other. The first group is connected with the first plenum chamber. The second group is connected with the second plenum chamber.
In accordance with a still further aspect of the present invention, an air intake method is provided for a multi-cylinder engine that has first and second plenum chambers, and at least two intake passages, per each one of the first and second plenum chambers, that connect the first and second plenum chambers with respective cylinders of the engine. The method comprises delivering air to one of the cylinders from the first plenum chamber, delivering air to another one of the cylinders from the second plenum chamber, and delivering air to a further one of the cylinders from the first plenum chamber.